The present invention relates to a fuel injection apparatus for internal combustion engines, and more particularly to a fuel injection apparatus which is able to adjust the amount of fuel injected with high accuracy without increasing manufacturing cost and which is especially preferable for use as a unit injector.
An apparatus for improving the accuracy of the adjustment of the amount of fuel injected by a fuel injection apparatus for internal combustion engines is disclosed in Japanese Patent Application Public Disclosure No. 38631/82, in which the quantity of fuel intake is controlled by controlling the opening period of a solenoid valve provided on the fuel intake side of a fuel injection pump and the cut-off fuel is again taken in from a cut-off part of the fuel injection pump. In order to improve the accuracy of the adjustment of the fuel quantity, this proposed apparatus is constructed taking account of the fact that the amount of intake fuel adjusted by the solenoid valve is injected as it is when the cut-off fuel is again taken in at the fuel-intake storke.
However, in the proposed apparatus, since the adjustment of fuel quantity is carried out by the solenoid valve, which operates in synchronization with the intake stroke of the fuel injection pump, the accuracy of the adjustment of fuel quantity depends upon the operating performance of the solenoid valve, e.g. on the response characteristics and the like of the solenoid valve. Thus, to increase the accuracy of the adjustment of the fuel quantity, it is necessary to use a relatively expensive solenoid valve with high response characteristics, so that the manufacturing cost is liable to increase and miniaturization of the apparatus becomes difficult.